(1) Field of the Invention
The present invention relates to a curable rubber composition. More particularly, the present invention relates to a curable rubber composition having an excellent strength, abrasion resistance, and resistance to compression set.
(2) Description of the Related Art
The incorporation of zinc dimethacrylate and/or basic zinc methacrylate in a rubber is well known. For example, British Patent No. 1,091,818 teaches that a rubber having an excellent strength can be obtained by incorporating a metal salt of dimethacrylic acid and an organic peroxide in an ethylene/propylene rubber, and crosslinking the composition; British Patent No. 159,477 discloses a golf ball having a core composed of a rubber obtained by mixing basic zinc methacrylate (zinc oxide/methacrylic acid molar ratio=1/1 to 1.5/1) into a polybutadiene rubber and curing the rubber with a radical generator; Japanese Unexamined Patent Publication No.59-149938 teaches that a product obtained by incorporating zinc dimethacrylate particles having a surface area of about 3.7 to about 5.4 m.sup.2 /g and carbon black, silica or clay, and curing the composition with a peroxide curing agent has an excellent strength; and Japanese Unexamined Patent Publication No. 52-121653 teaches that a composition having an excellent abrasion resistance is obtained by mixing polybutadiene with methacrylic acid and curing the mixture with a peroxide.
Nevertheless, the products disclosed in these patent references have a tensile strength lower than 300 kg/cm.sup.2, and moreover, a reference to an ethylenically unsaturated nitrile/conjugated diene type highly saturated rubber cannot be found in any of these patent references.